Purification of gases from unwanted impurities is one of the most important applications of getter (in other words, purification) materials. The requirements to purification materials used in gas purifiers are diverse and can vary but still there are three problems, which are always actual:                increase of sorption capacity of the gas sorbent;        maintenance of the material performance in case of operational failures or breakdowns;        simplification of the gas sorbent production technology and the reduction of the price for the end product.        
These problems are solved by the right choice of a getter material, shaping it into the form and structure, which are preferable from the point of view of the sorption process and also by improvement of the methods of manufacturing of the given materials.
Many high-melting transition metals, rare-earth metals, and also chemically active lithium and barium refer to metals, which are effective in capturing gases. Lithium and barium are unsurpassed gas sorbents, although their usage is avoided because of their high reactivity. The modern getters are based on Ti, V, Zr and Ni, which are more stable in the atmosphere and safe in a compact and dense form.
Metals sorb gases either by dissolving them in their lattice, or reacting with them and forming a layer of chemical compounds on the surface. However, under any sorption mechanism, the fraction of the getter mass involved in the process depends on the size of the active particles and the smaller the particles the higher is the really achieved sorption capacity. Therefore all getter materials are used in a highly dispersed state: films in vacuum applications and powders in gas purification.
The disadvantages of fine metal powders, especially of the powders of a nanometer range, are well known: these are the tendency of the powder particles to coagulation and coalescence and also their high chemical activity. To avoid the first one the volume concentration of nanoparticles is significantly decreased, “diluting” them by another, additional, material. Such dilution is achieved either in mixtures of getter particles with oxides particles [Weber D. K., Vergani G. U.S. Pat. No. 6,521,192, Feb. 18, 2003], or by partial introduction of nanoparticles into the pores of the base sintered material [Zeller R., Vroman C. U.S. Pat. No. 7,112,237, Sep. 26, 2006], or by deposition of metallic nanoparticles onto the surface of an inorganic support carrier material [Succi M., Solcia C. U.S. Pat. No. 6,436,352, Aug. 20, 2002], or by reduction of oxide nanoparticles, which are located on the substrate surface, to a partially metallic state in a flow of a reductant gas [Alvarez, Jr. D. U.S. Pat. No. 6,241,955, Jun. 5, 2001], etc. The sorption capacity of 1 cm3 of mixtures or composites of this type is by many times lower, than of the getter material itself, and their manufacturing technology is very complicated.
As regards the high reactivity of metallic nanopowders, the question arises here about how much reasonable the current relation is between the technical result of purification and the price for it. If nanopowders, e.g. Ti or Ni, immediately burn in the air, than in what way do they surpass Li or Ba, which to all that work better as gas sorbents?
So, as far as a seal failure in the gas system and an ingress of air inside a gas purifier with Ni powder completely disables the latter, and at normal depletion of the gas sorbent resource it is necessary to perform expensive regeneration of the material, then it seems quite reasonable to substitute the transition metals for more active materials, though limited to a single use, but cheap and having high sorption capacity. The recently found [Chuntonov K., Voronin G. F., Malyshev O. B. US Pat. Application 20070196256, Aug. 23, 2007; Chuntonov K., Setina J., New lithium gas sorbents: I. The evaporable variant. J. Alloys Compd., 455, (2008), p. 489] ability of concentrated solid solutions of Li in Ag, Cu and in some other corrosion-resistant metals to self-passivation supports those reasons and makes it possible to develop safe getters with a very high sorption capacity. It is quite clear, that the development of the new getters of this type should start with the creation of a high porous gas-permeable structure.
From the known methods of production of getter alloys with high surface area the most commonly used is the technology of pressing the metallic powders and further sintering the pressed powder in vacuum [Ferrario B., Figini A., Borghi. Vacuum 35 (1984) 13; Reutova N. P., Maneghin S. J., Pustovoit J. M., Stoljarov V. L., Akimenko V. B. U.S. Pat. No. 6,322,720, Nov. 27, 2001], However this technology is inapplicable to solid solutions Ag—Li, Cu—Li etc. due to their softness and ductility, which not only impede the production of such powders, but also make their further thermo-mechanical treatment impossible.
The most suitable method of loosening the structure of lithium alloys is the sublimation method [Chuntonov K. US Pat. Application 20060225817, Oct. 12, 2006; Chuntonov K., Ipser H., Richter K. EP1821328, Feb. 10, 2006], which was recently successfully applied to rapidly cooled eutectic alloys. According to this method an alloy, containing a nonvolatile phase with a developed dendritic carcass as a structural basis and a volatile phase as an addition, which fills the space between the dendritic arms of the first one, is heated not going beyond the range of subsolidus temperatures to remove the volatile phase. As a result a solid residue in a form of a dendritic skeleton with end-to-end channels, along which gases can penetrate into the depth of the material, is formed.
The problem, however, is that the sublimation method according to the cited documents, is effective only when it is applied to binary, ternary or multi-phase alloys, but not to single phase ones like solid solutions Li-Me, where Me=Ag, Au, Co, Cu, and Mg. It is also necessary to have in mind that from the mentioned metals Me the first two, Ag and Au, belong to noble ones, while the next two, Co and Cu, melt under the temperatures close to or even higher than the boiling point of lithium, which makes metallurgical procedures with them more difficult.
It follows from the above said, that two problems have to be solved for the creation of high porous gas sorbents on the basis of passivating Li-Me alloys:
1. To adjust the alloys of solid solution of lithium type to the sublimation method, so that after quenching of the melt and the further vacuum evaporation of the volatile constituent, a passivated or able to passivation dendritic carcass of the material with high lithium concentration should appear.
2. To optimize the adapted according to item 1 alloy composition, so that that the price for the end product should be maximally reduced and the process for its production—maximally simplified without damaging its sorption properties.
The solution for these problems for the case of Li-containing sphere-like particles in the range from several tenth of a millimeter to several millimeters in diameter is given below. These particles with the dendritic structure promise to become an ideal purification material for gas purifiers in the temperature range from room temperature to ˜250° C.